Fix 4XX errors incorrectly categorized as 5XX in PDF splitting (#290)

All of the retry configs look like these:
-
[general.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/general.py#L217-L218):
`retry_config = (retries, ["5xx"])`
-
[destinations.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/destinations.py#L182-L183):
`retry_config = (retries, ["5xx"])`
-
[sources.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/sources.py#L183-L184):
`retry_config = (retries, ["5xx"])`
-
[workflows.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/workflows.py#L75-76):
`retry_config = (retries, ["5xx"])`
-
[jobs.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/jobs.py#L175-L176):
`retry_config = (retries, ["5xx"])`
-
[users.py](https://github.com/Unstructured-IO/unstructured-python-client/blob/main/src/unstructured_client/users.py#L236-L236):
`retry_config = (retries, ["5xx"])`

This doesn't include all, but I do not see any cases where we would be
retrying on a 4XX.

Author: CyMule

src/unstructured_client/_hooks/custom/split_pdf_hook.py

@@ -669,11 +669,8 @@ def after_success(
         elements = self._await_elements(operation_id)
 
         # if fails are disallowed, return the first failed response
-        # Note(austin): Stick a 500 status code in here so the SDK
-        # does not trigger its own retry logic
         if not self.allow_failed and self.api_failed_responses.get(operation_id):
             failure_response = self.api_failed_responses[operation_id][0]
-            failure_response.status_code = 500
 
             self._clear_operation(operation_id)
             return failure_response